Not really. Humans are. We hunt them mercilessly and have the technology to take them out in great numbers. Other than humans, sharks may be the largest threat, as they are among the few species in the seas that can bite a turtle and kill it.
On land there are a number of animals, hyenas, wild dogs, etc. that can also threaten adult nesting females and their eggs. When the turtles are younger, however, they are threatened by just about every predatory fish, and to a small extent birds and crabs.












